1. Field of the Invention
The present invention relates to a touch panel.
2. Discussion of Background
Electronic devices, such as a cellular telephone, a smart phone and a PDA (personal digital assistant), have a limited area for placing an input unit, such as a switch or a digital keypad since they are required to have a large screen. Further, it is required to realize information input measures which a user can input information in an easy-to-understand manner by touching a display image while seeing the image displayed on the display element, such as a liquid crystal display.
Thus, a demand to provide a display with a touch panel has recently increased.
A touch panel is placed on a display element, such as such an above-mentioned liquid crystal display, and is a generic term of input units, which detect where a touch is made, when a user touches an operation screen by his or her finger, a pen or the like. The system for detecting where a touch is made is classified into a resistive touch film system, a capacitive touch system and the like.
In such a resistive touch film system, two substrates, each of which has transparent electrodes thereon, are disposed so as to be spaced from each other with the transparent electrodes on both substrates confronting. In other words, it is difficult to reduce the thickness since such two substrates are needed. Conventional resistive touch film panels are configured such that a substrate is pressed to short-circuit opposed electrodes. For this reason, such conventional resistive touch film panels have a low durability because wear or the like is likely to be caused.
On the other hand, such a capacitive touch system is particularly appropriate to portable electronic devices because of being capable of being configured so as to employ a single substrate, reducing the thickness. In this system, a projected capacitive touch system has been frequently employed.
In such a projected capacitive touch system, a user's finger serves as ground since the user works as an electrical conductor. In other words, when a finger is brought close to a sensing electrode disposed on the substrate of a touch panel, a capacitance is formed between the finger and the electrode, and such a capacitance change is detected by, e.g. a control circuit. In this case, it is not necessary for the finger to be brought into direct contact with the sensing electrode since the proximity of the user's finger is detected as such a capacitance change.
Such a projected capacitive touch system needs to be subjected to patterning of transparent sensing electrodes for detection. Recently, the most frequently used technology is to disposes X-electrodes extending in an X-direction and Y-electrodes extending in a Y-direction in a lattice pattern on one side of a substrate.
JP-A-60-75927 discloses a capacitive tough panel technology where a plurality of X-transparent conductive strips (X-electrodes) and a plurality of Y-transparent conductive strips (Y-electrodes) are disposed on a transparent substrate, such as a glass substrate, so as to be isolated through an insulating film.
In such a projected capacitive touch system, it is necessary to dispose an electrode and an electrode so as to cross each other on a glass substrate forming a touch panel as disclosed in JP-A-60-75927.
With regard to the connection structure between both electrodes in such a case, e.g. JP-A-2008-310550 discloses a configuration example of a capacitive input unit, which includes a first transparent electrode pattern and a second transparent electrode pattern disposed on one side of a transparent substrate, wherein the second transparent electrode pattern, which is interrupted at portions where both patterns cross each other, is electrically connected by a relay electrode disposed as an upper layer on an interlayer insulating film at each of the crossing portions.